[The physiology of natural parturition in cows].

In the year 1990 free parturitions of 339 cows were followed on three farms; these parturitions were compared with the last parturitions of these cows when the tender's assistance was available. The spontaneous free parturitions were followed in the open air in litter boxes which were located outside the barns where the groups of about twenty highly pregnant cows and heifers were housed for two months before their parturitions all the year round irrespective of the weather conditions. In addition to direct continuous observations, a host of zooveterinary data filed for these groups of animals were evaluated, concerning particularly those animals which could not be directly followed for the time reasons. Through direct observations the time schedule of the given parturition was evaluated and recorded above all, including all changes in the behaviour of the cow itself, and also behavioural changes in the group of animals or the behaviour of particular groups of animals toward each other. Applying the same criteria, the behaviour of born calves toward the mother, behaviour of calves toward each other and their behaviour toward other breeding cows was evaluated. The method of disinterested observation was used, this means the principle of noninterference with the most actions observed, with the exception of such situations that could result in the calf death. Another principle was to minimize through these observations all negative effects that could influence the behaviour of individual animals and also the behaviour of the whole group.(ABSTRACT TRUNCATED AT 250 WORDS)